ok, profpf, there’s a few things you can try… reset the smc and zap PRAM on startup.. here’s how to do that ( Assuming the Apple communities admin doesn’t consider this an inappropriate link and strike out my post-you never know)
anyways, here / Reset the SMC of your Mac - Apple Support
and here/ Reset NVRAM on your Mac - Apple Support
i usually like to do the 2nd one by holding down the 4 key combo for 3-4 chimes then let go… maybe run Apple Diagnostics… or disk first aid.. here’s for the first one /
Use Apple Diagnostics to test your Mac - Apple Support (CA)
anyways for the 2nd one you have to boot up from your recovery partition , assuming you have Lion ( macOS 10.7) or later on it… then get to Mac OS X tools and run disk utility… to get that started, restart your Mac, holding down the Apple+ R keys together until you see a languages screen, pick one and keep going… move your cursor ( the arrow ) to
the top center of your screen and click.. you should now see Mac OS X tools.. from there, disk utility… dumb question to ask but, do you have a backup/have you done a backup kinda recently ? .. eg Time Machine… if you do, you might be OK , but if not/ If never… “what’s a backup, what’s Time Machine?” Then you might have a problem.. any-hew, run Apple diagnostics after trying those other things and then add to your post ..
John B